Deafening Smite

With a peal of thunder, heard up to 600 feet away, the target takes 2d8 Thunder damage.  

They are forced to make a Constitution saving throw.  On a failed save, the affected creature is Stunned, Deafened and Silenced, unable to speak or cast spells requiring a verbal component.  This effect lasts until the end of your next turn.    

At higher spell levels.  For every level above 1, the damage increases by 1d8.